1. Field of the Invention
The present invention relates to a bucket equipped with a mixing device for use in work for improving the soil of grounds such as road grounds, to an excavation machine having such a bucket, and to a soil improvement method using such an excavation machine.
2. Related Prior Art
Improvement work for improving certain grounds such as roadbeds or poor grounds has been hitherto performed, in which soil having poor properties is mixed with materials such as cement or lime to thereby convert the grounds into grounds with strong properties.
Recently, in such ground improvement work, instead of a method in which soil whose properties have already been improved in a remote soil-improvement plant is buried at the site, another method has come into frequent use. In the second method, a surface layer of the ground is directly solidified in situ. For this purpose, a special category of machines is used at the site: a mixing machine, such as a stabilizer, shown in FIG. 12.
The second method will be described with reference to FIG. 12. First, a prescribed solidifying agent is sprayed on the site of the soil improvement work. Then, the stabilizer is caused to travel over the agent-applied ground in the direction A shown in FIG. 12. A work machine rotor, provided at a rear portion of the stabilizer, is caused to excavate the ground, thereby mixing the soil of the excavated ground with the sprayed solidifying agent. Thus, the soil of the ground is improved.
However, grounds such as roadbeds for ordinary roads and grounds for building areas generally have underground structures buried therein, such as electricity and telephone cables, and water and gas supply pipes. In addition, associated facilities, such as manholes, are provided underground.
Therefore, when performing ground improvement work with a stabilizer on the surface of grounds having such underground obstacles, the work must be performed while underground structures are detected. As a result, the work entails a high risk of damaging underground structures, and low operational efficiency. Another disadvantage is that a mixing operation may not be completely performed since improvement work is sometimes restrained for the sake of safety near underground structures which might be damaged. As a result, the work may leave many portions of the ground unimproved, and thus, fail to assure thorough improvement.
After spraying the solidifying agent, the stabilizer travels on crawlers or wheels over the sprayed solidifying agent. This is disadvantageous in that some of the agent is scattered, contaminating the work environment.